“Based on a true story.” The Toronto International Film Festival is full of these fact-based movies: Mandela, 12 Years a Slave (19th-century free black Solomon Northup), The Fifth Estate (Julian Assange), Rush (race car rivals James Hunt and Niki Lauda), The Railway Man (Japanese torture camp survivor Eric Lomax) and Parkland (tracing the events at a Dallas hospital on Nov. 22, 1963). From the antebellum American South to modern South Africa, from World War II to WikiLeaks, from JFK to Formula 1, inspirational or just informational historical dramas are crowding the Toronto schedule this year.

Actually, this year and every year — because TIFF is a showcase for Oscar-wannabe films, and nothing appeals to the members of the Motion Picture Academy quite so much as a true story rouged into a stirring drama. Since 2000, bio-pics have accounted for 21 of the Best Picture nominees and two of the last three winners, The King’s Speech and Argo. The genre is even more generous to performers. Seven of the past 11 Best Actor awards, and eight Best Actresses, have gone to people playing real people. These winners have portrayed heads of state (Helen Mirren as Queen Elizabeth II, Colin Firth as King George VI, Forest Whitaker as Idi Amin Dada), prime ministers and presidents (Meryl Streep as Margaret Thatcher, Daniel Day-Lewis as Abraham Lincoln), novelists (Nicole Kidman as Virginia Woolf, Philip Seymour Hoffman as Truman Capote) and popular singers (Reese Witherspoon as June Carter Cash, Jamie Foxx as Ray Charles). It’s a hallowed Academy tradition: rewarding the famous for playing the famous.

So what’s so special about Ron Woodroof, the working-class Texan play by Matthew McConaughey in Jean-Marc Vallée’s grittily uplifting Dallas Buyers Club? He’s just a Texas electrician, a hard partier and drug user, a part-time rodeo rider and serial homophobe, who in 1985 learned he had contracted HIV (from sex with a drug-using woman). Told he had 30 days to live, and that AZT was the only drug that might stabilize his condition, Woodroof first paid a hospital employee to steal the stuff. Then, when one doctor warned him that “The only people AZT helps are the people selling it,” he researched treatments that the Food and Drug Administration had not yet approved. “Screw the FDA,” he tells the medical establishment, “I’m gonna be DOA.”

[SPOILER ALERT:Though most reviews have spilled the well-known facts of Woodroof’s life, and though you may want to know what the film’s title refers to, we urge anyone planning to see the film to skip this paragraph.] Traveling the world to find more promising drugs, he established the Dallas Buyers Club, whose members — mostly gays with HIV or full-blown AIDS — paid Woodroof for access to the pharmaceuticals that could prolong their lives. Like the Old Dope Peddler in Tom Lehrer’s song, this good ole boy did well by doing good. Woodroof lived for six years after his initial death notice, and some of the drugs he found and sold were later proved to be of help to AIDS patients. [END SPOILER ALERT.]

If anyone associated with Dallas Buyers Club is famous, it’s McConaughey, who lost way too much weight for the role. Vallée, on stage at the TIFF premiere, said “almost 50 pounds.” Thirty-eight is the official number, but either way, McConaughey wasn’t exactly a fatty to begin with. Actors, as we all know, are nuts; they’ll do anything for a role, including punishing their bodies. Robert De Niro gained 60 pounds to play the older Jake LaMotta in Martin Scorsese’s 1980 Raging Bull, and Christian Bale dropped 62 pounds (from 182 to 120) for his lead in the 2004 The Machinist. McConaughey’s weight loss — in the film he looks even gaunter and more ghostly than photos of the real Ron Woodroof — follows those spectacular stunts and provides as rich an emotional and artistic payoff as De Niro’s.

This is a bold, drastic and utterly persuasive inhabiting of a doomed fighter by a performer who has graduated from the shirtless rom-com Romeo of the last decade to indie-film actor du jour. His turns as a more reckless Dallas dude in Killer Joe, as the strip-club showman in Magic Mike, as a Texas D.A. in Bernie and as the lovelorn outlaw in Mud have led up to this, the apogee of an adventurous career change. (Blessedly, in Dallas Buyers Club we never see the emaciated Matthew with his shirt off.) Most of these roles run subversive variations on the wastrel charmer he played in The Wedding Planner, How to Lose a Guy in 10 Days and Ghosts of Girlfriends Past. The salesman patter of his musical voice remains, but it is directed to darker, more toxic ends.

Early in Dallas Buyers Club, written by Craig Borten and Melisa Wallack, Woodroof coarsely ingests the news of the first celebrity AIDS death: “Did you know Rock Hudson was a c—s—-r?” The lesson for Ron and many Americans was not that a new disease was killing people, but that a romantic Hollywood star was gay. He dismisses his diagnosis because he’s not queer, and insults the homosexuals at a meeting of HIV victims. Only when his coworkers hear of his illness, and paint the words FAGGOT BLOOD in red paint on the side of his house, does Ron realize he has more in common with the gays he despises than with his old pals.

Ron had recoiled from a transvestite druggie named Rayon (Jared Leto) when he occupied the hospital bed next to Ron’s. But who, homophile or homophobe, could resist the winsome Rayon? In a role that shares, and almost seizes, the film’s emotional center, Leto captures the sweet intensity and almost saintly good humor of a glamorous, poignant and downright divoon creature — a blithe Camille who may surrender her health but never her panache. Interrupting his movie career to write songs and tour with his band Thirty Seconds to Mars, Leto returns with a superb performance. At the TIFF premiere he noted that “it was five years, more like six,” between films, adding with a flirtatious smile. “How can you miss me if I never go away?”

Borten and Wallack based their script on hundreds of hours of interviews with Woodroof, then waited 20 years for the film to get made. Marc Forster was to direct Brad Pitt as Ron; Ryan Gosling was to star for director Craig Gillespie. The job finally went to Vallée, the French-Canadian director of the bright coming-of-age comedy C.R.A.Z.Y., the stately period piece The Young Victoria and, best of all, the swooningly romantic Café de Flore. Having made films in Quebec, London and Paris, Vallée quickly accommodated himself to urban Texas (played by New Orleans). Every scene seems lived-in, with a native’s familiarity and a foreigner’s eye for the telling detail.

Vallée gets excellent work from Steve Zahn as Ron’s brother, Griffin Dunne as a kindly, uncertified medico in Mexico (he looks like Jerry Garcia with a stethoscope) and Jennifer Garner as, basically, the good doctor who seeks new drugs for HIV and AIDS patients. (Denis O’Hare takes one for the team by playing the bad doctor who won’t give up his pharma grants and keeps pushing AZT.) If the camera occasionally suffers a fashionable case of the jitters, the movie transcends its agitated verismo to impart dramatic and behavioral truth. In a crowded field of based-on-a-true-story films at Toronto, Dallas Buyers Club is the real thing.